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Posted at 11:00 AM ET, 09/ 5/2008

Hanna Heading to Region With Heavy Rains, Wind

By Capital Weather Gang

Partly sunny today; wind-swept rain tomorrow

*Tropical Storm Warning issued for metro area and Eastern shore.*
*Flash Flood Watch for metro area Saturday morning through afternoon*

As partly to mostly sunny morning skies help area temperatures rise toward highs in the upper 80s today, Hanna inches closer to an early Saturday landfall along the North Carolina coast, either as a strong tropical storm or Category 1 hurricane. As Hanna approaches, this afternoon will bring increasing clouds with a 40% chance of some showers by early evening.

The main event comes overnight and tomorrow with heavy rains -- 2-4" inches in some areas with locally heavier amounts -- that could cause flooding in spots, and winds that could reach sustained speeds of near 35 mph and occasional gusts to around or above 50 mph. Overcast skies will limit highs tomorrow to the 70s.

RAINFALL MAP AND TIMELINE

5 PM FRI to 12 AM SAT
40% chance of showers. Winds sustained from the south and southeast at 10-20 mph.
12 AM SAT to 8 AM SAT
Frequent showers with a few thunderstorms. A couple periods of steady rain. Winds sustained from the northeast at 15-25 mph.
8 AM SAT to 6 PM SAT
Heavy rain bands move through with thunderstorms mixed in. Winds sustained at 20-35 mph. Gusts to 50 mph.
6 PM SAT to 9 PM SAT Steady rain tapers quickly from southwest to northeast. Scattered showers and thunderstorms linger. Winds sustained at 20-30 mph. Gusts to 40 mph.
After 9 PM
Clearing skies and decreasing winds.

USEFUL LINKS

How to Prepare for Flooding, Blackouts and High Winds | Track Hanna | Satellite image | Southeast radar | Northeast radar

STORM FAQ


Estimated sustained winds and gusts Saturday.

How strong will the winds be? Could there be wind damage and power outages?

Occasional strong gusts of over 50 mph could be capable of bringing down some trees and power lines. Scattered power outages are possible in the metro area. The most outages are likely to be near the Bay and to the east.

What precautions should I take?

No need to board up windows. Or alter your schedule today. But do ensure outdoor furniture and plants are secured and/or brought inside before you go to bed tonight. Does your sump pump work if your basement leaks? Have a flashlight handy in case the power goes out, and food and supplies that could last you and your family through a day or two without power, which is probably the worst-case scenario we would see with this storm.

How confident are you in your forecast?

Confidence is toward the high side because most computer models are in agreement on Hanna's track. It's doubtful the storm will miss us. There's a small chance it could veer further east than expected and thus leave us with less rain and slightly weaker winds. There is also the chance that Hanna tracks somewhat further west than forecast, shifting the areas of heaviest rain and strongest winds west.

Keep reading for answers to more FAQs about the storm, including the forecast into early next week.

What is the flooding threat?

Widespread, major flooding is not anticipated. But basements, roadways and other low-lying areas that are typically prone to flooding will be at risk, as Hanna could dump several inches of rain in a very short period of time.

Could there be a tidal surge along the Potomac?

The Weather Service is projecting two to four feet of storm surge along the western shore of the Chesapeake Bay and the tidal Potomac River on Saturday. The high tides to watch occur on Saturday morning and evening, but only minor coastal flooding is anticipated.

Could there be tornadoes?

An outbreak of tornadoes does not seem likely. However, it's not unusual for tropical systems to spawn at least a few tornadoes. Stay tuned to Capital Weather Gang during the storm. We'll let you know if any tornado warnings are issued by the National Weather Service.

When and where will the conditions be the worst?

Along and east of I-95, from sunrise through sunset Saturday.

How bad will this be at the Maryland/Delaware beaches?

Sustained winds of 40-60 mph and gusts to 70 mph could mean some flying debris, significant power outages and moderate beach erosion. Rainfall, on the other hand, should be less than here in the metro area. Probably no more than 1-2".

Will this be as bad as Isabel?

Not likely. Isabel produced sustained winds up to near 50 mph in parts of the area and gusts to near 80 mph. Hanna's winds will be weaker. Storm surges will also be lower with Hanna than they were with Isabel. There's a small chance Hanna intensifies a little before landfall which would bring winds closer to the levels of Isabel, but it's doubtful Hanna will close the gap.

When will the storm clear and what's the forecast for Sunday and beyond?

The rain should be over, or quickly coming to an end, and winds dissipating by Saturday evening, with clearing skies Saturday night and lows in the 60s. Sunday looks spectacular -- mostly sunny and breezy with highs in the upper 80s and decreasing humidity. Monday should also be nice, again mostly sunny with highs in the mid 80s and not too humid. Tuesday brings the next chance of showers and thunderstorms (about a 30-40% chance as of now) with a mix of sun and clouds and highs in the 80s.

By Capital Weather Gang  | September 5, 2008; 11:00 AM ET
Categories:  Forecasts, Tropical Weather  
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Next: Hanna Charging Towards Carolina Coast

Comments

Godspeed Hanna!!

Posted by: Brian in Alex | September 5, 2008 6:55 AM | Report abuse

We're preparing as we did for Isabel, though not with the boards on the windows, out in Chesapeake Beach. Generators are ready and supplies bought. We lose power at the drop of a hat here so I have no doubt it will be dark tomorrow and the surge of a few feet will be enough to make more than a few places flooded out.

Posted by: PenguinSix | September 5, 2008 7:00 AM | Report abuse

PenguinSix, sounds like you are very prudent with your precautions. Good luck and hang in there. Hopefully Hanna will speed up (as predicted) to become be a quickly moving system--and our area is only grazed by a rapid dose of wind/rain.

Posted by: Camden, Capital Weather Gang | September 5, 2008 7:09 AM | Report abuse

EXCELLENT write-up! This is why I keep coming back to CWG.

Posted by: Etta | September 5, 2008 7:34 AM | Report abuse

i live in the district, but i signed up to volunteer for a campaign in virginia about 45 min. down I-95 on saturday morning. would it be prudent to cancel due to weather, or am i being over-cautious?

Posted by: ellen | September 5, 2008 7:40 AM | Report abuse

Ellen, it depends on the campaign for which you are volunteering.

Posted by: Marc | September 5, 2008 8:36 AM | Report abuse

Along the lines of Ellen's question, I have a relative scheduled to drive to visit me in Silver Spring from NJ. So she will be traveling down the I-95 corridor early Saturday morning.... better to cancel?

Posted by: gotaquestion | September 5, 2008 9:14 AM | Report abuse

"The chance that it would give us more rain and stronger winds than forecast is even smaller."
I assume you meant to say that "The chance it would give us more rain and stronger winds than a more easterly foreast is even smaller"?

Posted by: Paul - Sterling | September 5, 2008 9:29 AM | Report abuse

Ellen and gotaquestion: Wind swept heavy rain is likely Saturday morning along I-95. I don't think it would be the best time to travel and traveling in this kind of weather increases risk, but I think roads will be passable.

Posted by: Capital Weather Gang | September 5, 2008 9:32 AM | Report abuse

At 980 mb how can Hanna be a tropical storm? I fear that Hanna will continue to strengthen and folks on the coast (NC) will be caught off guard.

What does the team think?

Posted by: Mike | September 5, 2008 9:36 AM | Report abuse

*Agree with Etta, real nice, concise write-up, best one out there!
*LWX pushed the Flood Watch further west (at 852am) to include areas of the Blue Ridge and Shen Valley-whoo hoo.....

Posted by: Mike from the Blue Ridge | September 5, 2008 9:45 AM | Report abuse

Paul: You're right... that statement was unclear and doesn't even reflect our current thinking. It has been edited to say " There is also the chance that Hanna tracks somewhat further west than forecast, shifting the areas of heaviest rain and strongest winds west."

Posted by: Capital Weather Gang | September 5, 2008 9:46 AM | Report abuse

Thanks CWG. I've been reading your blog for a long time now, thanks for all your hard work!

Posted by: gotaquestion | September 5, 2008 9:54 AM | Report abuse

I asked yesterday and didn't get a response -- what's the outlook for the Virginia Beach area?

Posted by: Doc | September 5, 2008 10:13 AM | Report abuse

I'm expecting a friend to arrive BWI from Winston-Salem, NC tomorrow around 7pm. What are the chances of a canceled/delayed flight with this storm? And I agree - fantastic write-up, thank you!

Posted by: Saturday Flights | September 5, 2008 10:44 AM | Report abuse

Thanks for being so open to highly personalized questions (talk about hyperlocal journalism) ... so here's one:

My family and I are finishing off what's been a near-perfect week in Bethany Beach. Our rental goes to 10 a.m. tomorrow (Saturday). If I had my druthers I'd pack up and head home tonight, but I'm with my in-laws, so the druthers aren't my own.

It looks like if we were to drive home to DC between, say, 8 a.m. and 11 a.m. tomorrow, we'd certainly drive through nasty weather but maybe miss "the worst." Or at least that's my reading of the latest hourly estimates. I know there are no guarantees, but what would your best guess be? Thank you!

Posted by: DCbeach | September 5, 2008 10:52 AM | Report abuse

The Tropical Storm Watch has become a Tropical Storm Warning with the 11am package.

Posted by: Ian, Capital Weather Gang | September 5, 2008 10:53 AM | Report abuse

My wife is scheduled to depart DCA at 10AM tomorrow (Saturday), and we're wondering what it will be like for flights. It seems that delays will be inevitable, but cancellations? Nothing from the airlines as yet...

Thanks!

Posted by: More Saturday Flights | September 5, 2008 10:58 AM | Report abuse

MoreSat: It depends on the wind. I know, well, duh, but more importantly the direction of the wind at the time of departure. Most pilots won't take off with a 10 knot tailwind, and airports won't operate with a 30 knot crosswind. With DCA having multiple runways in different directions, flights will be able to get off the ground, but they may not be able to operate more than one runway, which would give you delays.

Then there's the issue of how bumpy the ride will be, but that's another story....

Posted by: John | September 5, 2008 11:07 AM | Report abuse

Also just checked a couple of airline web sites--the travel advisories were not up to DCA just yet. Some of them had Norfolk and Richmond, but the Big Three weren't there. I imagine that this will change later today now that we have the warning.

Posted by: John | September 5, 2008 11:11 AM | Report abuse

I think you guys have the best information in the entire WaPo - timely and pretty darn accurate.

One thing I've noticed when a big storm is coming is the lack of tide and surge info from the local media for boaters in the area (and there are lots of us.) And it appears that you are cognizant of and covering that also.

Thanks!

Posted by: waterfrontproperty | September 5, 2008 11:13 AM | Report abuse

I would guess there will at least be a fair amount of significant delays, especially with flights travelling up and down the east coast. This storm will hit almost everyone in the i-95 corridor from SC to ME tonight and tomorrow.

Posted by: Ian, Capital Weather Gang | September 5, 2008 11:14 AM | Report abuse

So if we were sitting right in the same location this far out from a tropical storm without access to satellite technology, cool computer models, modern forecasting science, or long distance communication, would we know a tropical storm was coming yet?

I'm just wondering how much advance warning people had before a tropical event back in the day. I can't feel much of a noticeable difference in the air today (with the exception of a few days of excessive heat and humidity, which would have me suspicious that SOME weather event was coming). Do the clouds right now at midday warn anything? Does the air feel "tropical?" The wind? Maybe people used to be more sensitive to the specific physical signs of oncoming tropical weather than the average person is now?

Discuss.

Posted by: Laura in NWDC | September 5, 2008 11:18 AM | Report abuse

For some bizarre reason, our area in Arlington seems to lose power at the drop of a hat (Thanks a lot, Dominion Power!). Rain, no rain. Thunder, no thunder. Doesn't matter. Very frustrating. And I'm not even going to THINK about bad a** Ike.

Posted by: twisted diva | September 5, 2008 11:20 AM | Report abuse

Accuweather still saying 1.58" this weekend, TWC says 1-2"

Posted by: steve takoma park md | September 5, 2008 11:21 AM | Report abuse

I would almost guarantee that there will be very lengthy delays at all the area airports throughout the day tomorrow. Definately not the best way to travel. Try to call your airlines and see if an alternate flight is available. I would also advise against any unrequired travel with the chances of trees/powerlines down. As it is, I have to drive from Columbia to Suitland tomorrow to work, and I'm not very happy about it.

Posted by: Brian, Capital Weather Gang | September 5, 2008 11:24 AM | Report abuse

Laura, the advent of satellite monitoring has GREATLY helped our ability to monitor tropical storms. Before them, meteorologists relied mostly on ship reports which were spotty at best. Some things that might tip off the approach of a tropical storm to our area may be: Obviously a drop in barometric pressure, increase in dew point/humidity, High and Mid-level clouds approaching from the East and Southeast, and the wind also increasing from the east or southeast. Still, without knowing a storm was apporaching, any normal person would probably not even notice these conditions as anything abnormal until the actual storm was very close.

Posted by: Brian, Capital Weather Gang | September 5, 2008 11:34 AM | Report abuse

Will it be safe to drive? Planning on going to Philadelphia tomorrow am. Will is extend up there?

Posted by: MD | September 5, 2008 11:36 AM | Report abuse

forecast and models seem to be trending west. nhc's 1100 posting reflects that

Posted by: Peter L | September 5, 2008 11:41 AM | Report abuse

Capital Weather Gang = the boss of all other D.C. area weather resources

Posted by: Lindemann | September 5, 2008 11:42 AM | Report abuse

I agree, commendations on the excellent information. The 'FAQ' was very helpful, also I really liked the confidence indicator.

Posted by: Scott | September 5, 2008 11:55 AM | Report abuse

Brian, this is fun for me (for now) because I've never experienced any sort of tropical weather and I'm learning a lot. Thanks for your help. I see what you're talking about from my high rise window - high clouds are definitely streaming in from the SE with breeze.

I guess there aren't that many situations when the clouds would otherwise move in from the SE.

Posted by: Laura in NWDC | September 5, 2008 11:57 AM | Report abuse

What might the outlook be for driving from Alexandria to BWI around 6 AM tomorrow?

I'm assuming it will suck, but will it at least be safe?

Posted by: alexandrian | September 5, 2008 12:15 PM | Report abuse

I am planning on driving from Philadephia to DC tonight, and then onward to visit family in Virginia Beach tomorrow morning. Do you think I will encounter significant issues with wind/visibility/traffic etc? Is it more reasonable for me to travel to DC tonight, and perhaps delay the VA Beach leg of the journey until Saturday evening? Or should I just scrap the whole weekend and stay put?

Posted by: TK | September 5, 2008 12:19 PM | Report abuse

Alexandrian-- Recommend making a game time decision based on how bad it is. Generally would not advise driving in heavy rain and 30+mph winds, but this doesn't mean you can't do it... it just means you're assuming a greater risk.

TK: Travel should be mainly ok tonight, but the earlier you leave the better. Recommend delaying the Va beach leg of the trip until late Saturday. But check conditions in the morning.

Posted by: Capital Weather Gang | September 5, 2008 12:26 PM | Report abuse

TK, from what I'm hearing, you could come to DC tonight and then delay the VA beach leg until just Saturday afternoon. It sounds like you could leave by 4 (maybe earlier!) on Saturday and since you're driving south you'd be out of the storm pretty quick. I don't know what I'm talking about though. I'm just going by what I've been reading on CWG today and yesterday.

Posted by: Laura in NWDC | September 5, 2008 12:27 PM | Report abuse

Earlier I talked about the wind direction affecting airport operations. Idiot me didn't bother to look at the forecasts at that time! :-)

With an east wind for much of Saturday morning and afternoon, the crosswind will make for dicey operations at DCA. IAD may not be able to use their parallel runways due to the direct crosswind they would get. Similarly BWI would be down to one runway as well. And all of that assumes that the airlines (and the captains!) feel secure about putting customers through those winds while on approach or climb out.

I'm surprised that the airlines haven't extended their advisories (read: more liberal ticket policies) to IAD or DCA yet.

Posted by: John | September 5, 2008 1:39 PM | Report abuse

I appreciate this plain-English explanation. I tried going to Accuweather.com to look at the long string of National Weather Service alerts and it all turns to gibberish for me. This is what papers need to do more of in the future to succeed -- localize.

Posted by: Bitter Bill | September 5, 2008 2:32 PM | Report abuse

Thanks for the great analysis. I do wish that there was a time/date stamp on it, especially the graphics, so we could know if they were updated after each round of NWS forecasts.

Posted by: Murph | September 5, 2008 5:36 PM | Report abuse

We are in Rehoboth and have heard that officials may close the Bay Bridge tomorrow if winds are high enough. Just be prepared.

Posted by: DCbeach | September 5, 2008 5:38 PM | Report abuse

Sorry - I meant to address my post above to DCbeach but put his name in the wrong spot. Apologies

Posted by: spf | September 5, 2008 5:39 PM | Report abuse

The comments to this entry are closed.

 
 
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